1. Field of the Invention
The present invention relates to a liquid crystal light valve, and, particularly, to a liquid crystal light valve which is suitable for a high-speed response type liquid crystal printer.
2. Description of the Prior Art
As information processing has been made higher in speed and made larger in capacity, printers have been required to have high printing quality. As printers in accord with the requirement, there have been developed a laser printer, a LED printer, a liquid crystal printer, etc. Particularly, the liquid crystal printer is not restricted with respect to the kind of light source as well as the wavelength thereof since the light source of the printer is provided independent of the printer. In comparison with the LED printer, etc., the liquid crystal printer has such advantages that the design of a photosensitive drum or the like is simple and the total cost of a printer system is therefore low.
As a liquid crystal printer, a double-frequency driven printer in which a high frequency and a low frequency are changed over in an on-period and an off-period respectively, is available on the market now. In the printer of this type, it is required to selectively apply two kinds of frequencies, which makes the driving system complicated. On the contrary, a high-speed response type liquid crystal light valve employing ferroelectric liquid crystals can be driven in a direct-current electric field and can be operated by a simple driving system. As to those ferroelectric liquid crystal light valves, some examples have been reported, but most ferroelectric liquid crystals have been chemically unstable at room temperature and nothing has been practicable.